From Halopedia, the Halo wiki
EOD-class Mjolnir (Explosive Ordnance Disposal), also designated as the MJOLNIR Powered Assault Armor/EOD variant, is a MJOLNIR armor variant originally designed by Materials Group, with the GEN2 version being manufactured by the Naphtali Contractor Corporation.
The helmet was designed to channel the pressure wave of a nearby detonation around the user's head, significantly reducing the likelihood of decapitation in the event of an explosion. The MJOLNIR/EOD variant's pauldrons and chest plate were designed specifically to reduce the number of grabbing edges on the armor, decreasing the likelihood of dismemberment and protecting Spartans during operations that involve the handling of explosive ordnance (e.g., clearing/planting land mines, demolishing enemy structures/material and, or planting/defusing bombs). The helmet can be fitted with the AN/PZY-6011Y TYPHON and AN/PCK-221 FARNDALE Command Network Modules, the Type E3 UA module and a CBRN module.
The MJOLNIR/EOD variant was originally created at the UNSC Damascus Materials Testing Facility on Chi Ceti 4. The EOD variant is speculated to have been developed in response to the death of Samuel-034 (the first Spartan killed in action) in November 2525. As late as 2558 the GEN1 version of the EOD helmet could be requisitioned by Spartan Operations personnel for use with their GEN2 Mjolnir suits.
EOD is fielded by Spartans deep in enemy lines, allowing them to navigate dangerous territory to disable or destroy enemy mines before the UNSC properly arrived. In the post-war era, the GEN1 EOD set, specifically the helmet, is still favored by Spartan combat divers and pioneers tasked with demolition roles.
The helmet has a pressure-resistant hardened rebreather unit. The reactor has alternating heat-tempered balance drives. The pauldrons are flow-distributing ceramic plates. The GEN2 kit also includes anterior torque couplings.
In 2554, Abilene's Naphtali Contractor Corporation took control over the EOD armor's production, and adjusted the systems plate configuration to reduce the potential for dismemberment during explosive ordnance activity and facilitation. It was tested at the Buffalo Breaker Yards. They proposed numerous enhancements to the armor's systematic approach to the GEN2 framework.
Halo 3 - Mark VI GEN1
The Bungie Armor is a slight variation of the EOD chestpiece. Bungie Armor lacks the three mid-level lights and has an effect that causes flames to appear around the helmet.
Halo: Reach - Mark V GEN1
The EOD helmet returns in Halo: Reach, though it features some minor different aesthetics than the Mark VI EOD helmet seen in Halo 3. All EOD helmet variants can be unlocked in the Halo: Reach's Armory through the game's purchase system via the use of cR. In Halo: The Master Chief Collection, the EOD helmet variants are attainable in the Season 1: Noble progression system.
Halo 4 - GEN2
EOD was one of the armor permutations to return, albeit completely redesigned for GEN2, in Halo 4. In The Master Chief Collection, the EOD set and its alternate Shadow (SHDW) variant are available by default.
Halo 5: Guardians - Upgraded GEN1
Non-canon and dubious canon appearances
Halo 4 and Halo Online
Halo: 5 Guardians
List of appearances